Electronic switches, such as a single pole multi-throw (SP×T) switch in an integrated circuit, grossly deviate from system characteristic impedance Zo, causing an impedance glitch, when they switch between states. Due to the severe impedance mismatch between system and switch ports during switching, signal reflections result in a high voltage standing wave ratio (VSWR).
In summary, impedance glitches slow down communication performance by temporarily disrupting data transmission and reception, pose reliability issues and cause a myriad of costs. Complex circuitry and/or programming are necessary to address problems caused by these glitches. Impedance glitches increase design, fabrication and operating costs given that the complex circuitry and/or programming consume manpower, die or circuit board area and power.
As an example, a switch may be used to select one of several voltage-controlled oscillators (VCOs) to control the modulating frequency coupled to a system. During switching, the impedance glitch initially load-pulls the VCO being selected, which changes its output frequency and causes the phase locked loop (PLL) to unlock. When this occurs, the system is unable to communicate until the loop recovers. Sophisticated circuitry and/or firmware/software programming development are required to overcome these interruptions. In another example, switching glitches in switched-power amplifiers may be detrimental to performance or even cause damage if sophisticated circuitry and/or programming are insufficient to counteract the glitches.
Thus, there is a need for an electronic switch that eliminates or substantially reduces impedance glitches to maintain constant or substantially constant impedance to improve performance, reliability and reduce manpower, circuitry and operating costs.